A pool can be filled by one pipe in 4 hours and by a second pipe in 6 hours. How long will it take using both pipes to fill the pool?

Question

A pool can be filled by one pipe in 4 hours and by a second pipe in 6 hours. How long will it take using both pipes to fill the pool?

Answer 1

pipe one fills 1/4 of the pool in 1 hour

pipe two fills 1/6 of the pool in 1 hour

x=# of hours together it takes the two pipes to fill the pool

(1/4)(x)+(1/6)(x)=1  (pool filled)

multiply both sides by the LCM which is 12

(12)(1/4)(x)+(12)(1/6)(x)=12

3x+2x=12

5x=12

x=12/5

x=2.4 hours or 2 hours and 24 minutes together